﻿using System;
using System.Collections.Generic;
using System.Web;
using System.Drawing;
using System.IO;

namespace HiLand.Utility.Drawing
{
    public class Thumbnail
    {
        /// <summary>
        /// 生成缩略图
        /// </summary>
        /// <param name="originalImagePath">源图路径（物理路径）</param>
        /// <param name="thumbnailPath">缩略图路径（物理路径）</param>
        /// <param name="width">缩略图宽度</param>
        /// <param name="height">缩略图高度</param>
        public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height)
        {
            MakeThumbnail(originalImagePath, thumbnailPath, width, height, ThumbnailCutModes.Cut);
        }

        /// <summary>
        /// 生成缩略图
        /// </summary>
        /// <param name="originalImagePath">源图路径（物理路径）</param>
        /// <param name="thumbnailPath">缩略图路径（物理路径）</param>
        /// <param name="width">缩略图宽度</param>
        /// <param name="height">缩略图高度</param>
        /// <param name="mode">生成缩略图的方式</param>    
        public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, ThumbnailCutModes thumbCutMode)
        {
            Image originalImage = Image.FromFile(originalImagePath);
            MakeThumbnailDetail(originalImage, thumbnailPath, width, height, thumbCutMode);
        }


        /// <summary>
        /// 生成缩略图
        /// </summary>
        /// <param name="originalImageStream">源图路径的数据流</param>
        /// <param name="thumbnailPath">缩略图路径（物理路径）</param>
        /// <param name="width">缩略图宽度</param>
        /// <param name="height">缩略图高度</param>
        public static void MakeThumbnail(Stream originalImageStream, string thumbnailPath, int width, int height)
        {
            Image originalImage = Image.FromStream(originalImageStream);
            MakeThumbnailDetail(originalImage, thumbnailPath, width, height, ThumbnailCutModes.Cut);
        }

        /// <summary>
        /// 生成缩略图
        /// </summary>
        /// <param name="originalImageStream">源图路径的数据流</param>
        /// <param name="thumbnailPath">缩略图路径（物理路径）</param>
        /// <param name="width">缩略图宽度</param>
        /// <param name="height">缩略图高度</param>
        /// <param name="mode">生成缩略图的方式</param>    
        public static void MakeThumbnail(Stream originalImageStream, string thumbnailPath, int width, int height, ThumbnailCutModes thumbCutMode)
        {
            Image originalImage = Image.FromStream(originalImageStream);
            MakeThumbnailDetail(originalImage, thumbnailPath, width, height, thumbCutMode);
        }

        private static void MakeThumbnailDetail(Image originalImage, string thumbnailPath, int width, int height, ThumbnailCutModes thumbCutMode)
        {
            bool isNeedCut = true;

            //约束的宽高
            int cw = width;
            int ch = height;

            int x = 0;
            int y = 0;

            //原图的宽高
            int ow = originalImage.Width;
            int oh = originalImage.Height;

            //新图的宽高
            int dw = width;
            int dh = height;

            switch (thumbCutMode)
            {
                case ThumbnailCutModes.HW://指定高宽缩放（可能变形）
                    if (cw > ow && ch > oh)
                    {
                        isNeedCut = false;
                    }
                    else
                    {
                        dw = cw;
                        dh = ch;
                    }
                    break;
                case ThumbnailCutModes.W://指定宽，高按比例                    
                    if (cw > ow)
                    {
                        isNeedCut = false;
                    }
                    else
                    {
                        dw = width;
                        dh = originalImage.Height * width / originalImage.Width;
                    }
                    break;
                case ThumbnailCutModes.H://指定高，宽按比例
                    if (ch > oh)
                    {
                        isNeedCut = false;
                    }
                    else
                    {
                        dh = height;
                        dw = originalImage.Width * height / originalImage.Height;
                    }
                    break;
                case ThumbnailCutModes.Cut://指定高宽裁减（不变形）    
                default:
                    if (ch > oh && cw > ow)
                    {
                        isNeedCut = false;
                    }
                    else
                    {
                        double or = (double)ow / (double)oh;
                        double cr = (double)cw / (double)ch;
                        if (or > cr)
                        {
                            dw = cw;
                            dh = oh * dw / ow;
                        }
                        else
                        {
                            dh = ch;
                            dw = ow * dh / oh;
                        }
                    }
                    break;
            }

            if (isNeedCut == false)
            {
                dw = ow;
                dh = oh;
            }

            //新建一个bmp图片
            Image bitmap = new System.Drawing.Bitmap(dw, dh);

            //新建一个画板
            Graphics g = System.Drawing.Graphics.FromImage(bitmap);

            //设置高质量插值法
            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

            //设置高质量,低速度呈现平滑程度
            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

            //清空画布并以透明背景色填充
            g.Clear(Color.Transparent);

            //在指定位置并且按指定大小绘制原图片的指定部分
            g.DrawImage(originalImage, new Rectangle(0, 0, dw, dh), new Rectangle(0, 0, ow, oh), GraphicsUnit.Pixel);

            try
            {
                //以jpg格式保存缩略图
                bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
            }
            catch (System.Exception e)
            {
                throw e;
            }
            finally
            {
                originalImage.Dispose();
                bitmap.Dispose();
                g.Dispose();
            }
        }
    }
}
